Blackchamois, its not oyster gray, but I think that grout color could be fantastic in another kitchen. Actually I know it would be fantastic, bc when I started looking for grout, its the color I wanted (ended up being too dark gray for my kitchen). I'm attaching the pic I first saw with it and the link of the kitchen. I really think its beautiful inthe right kitchen. My tiles are daltile, which have self spacers in them. You can find them in home depot (I had to special order my color)...they're made in the USA (except for the bullnose ones which are made in Mexico) Here is a link that might be useful: oyster grey

From what I understand from our contractor the tile dictates the grout size. I should add that because your tiles are larger and they are going on the floor, you may want to consider a 1/8" grout line. If we were talking about a uniform subway tile back splash - 1/16" grout line works (and I think are more preferable on vertical surfaces). 1/16" seems lean for that tile size. If your tile has variation even by a minute amount you will want a larger grout line. I am sure others will say 1/16" is doable, but it makes me nervous because you are depending so much on the skill level of your installer. I have 12 x 24 in my home and I did 3/16" and am very happy with them and feel like it looks very appropriate with the size of the tile.

I would door a darker grout to hide the grout lines so it looks more seamless.

It's hard to tell without the cabinet doors on but from what I see I'm thinking you should stay in the grey category